1. Field of the Invention
The present invention relates to a polymer optical waveguide in which an optical path of a light beam can be changed, and more particularly, to a method of manufacturing an optical integrated circuit, an optical-interconnection optical component, an optical-electrical circuit board, etc.
2. Description of the Related Art
As base members of optical components or optical fibers, inorganic materials such as quartz glass or multi-element glass characterized by a low transmission loss and a wide transmission band are widely used. However, since recently developed polymer materials have excellent machining properties and low cost in comparison with these inorganic materials, the polymer materials have received a lot of attention as materials for optical waveguides. For example, there has been provided a flat optical waveguide having a core-clad structure in which a core is formed out of a polymer having excellent transparency such as polymethylmethacrylate (PMMA) or polystyrene and a cladding is formed out of a polymer having a lower refractive index than that of the core material (Japanese Unexamined Patent Application Publication No. 3-188402). Alternatively, there has also been realized a low loss flat optical waveguide using polyimide which is a transparent polymer having a high thermal resistance (Japanese Unexamined Patent Application Publication No. 4-9807).
In view of the requirement for low cost, vertical cavity surface emitting lasers (VCSEL) are expected to be used in the field of optical interconnection, but when a laser beam to be emitted vertically to a substrate is incident on the optical waveguide parallel to the substrate, about a 90° change in the direction of the optical path is required. The polymer optical waveguide is cut at about 45° by a dicing saw, thereby enabling the 90° change of the optical path (see Patent Document 1: Japanese Unexamined Patent Application Publication No. 10-300961). However, when using the dicing saw, even unnecessary portions are cut out at 45°. For this reason, when using the dicing saw, it is impossible to form the optical coupling for the change of an optical path at any place in a substrate.
On the other hand, there was reported a method of forming a circular hole in an optically printed substrate using an excimer laser (Non-patent Document 1). The circular hole is equivalent to a micro lens, and the light usually diverges, so that the coupling efficiency is largely reduced. In order to enhance the coupling efficiency, complex asymmetric coupling optical systems are required, and it is necessary to arrange them in the order below micro meters. This is insubstantial in an optical-electrical circuit board.
Recently, decrease in size of optical components using the optical waveguide is required more and more. For this reason, it is necessary to bend, split, or couple the light over a short distance. Further, in the optical-electrical circuit board, it is necessary to arrange optical paths with the shortest distance at various positions. However, in the conventional curved optical waveguide or light coupling and splitting optical waveguide, it is impossible to form the optical waveguide to be smaller than a predetermined size or length due to restriction of a specific refractive-index difference. Therefore, there has been required an optical waveguide capable of decreasing the size of circuits.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 3-188402
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 4-9807
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 10-300961
[Non-patent Document 1] Paper of Japanese Institute of Electronic Information and Communications, 2001/September, Vol.J84-C No.9, pp. 724 to 725.